Analyte-triggered cascade signal amplification strategy for highly sensitive detection of iodate in table salt with dual-readout signals

Abstract

A novel and highly sensitive upconversion fluorescence and colorimetric dual readout iodate (IO3−) nanosensor system was constructed by using both the outstanding optical performance of NaYF4:Yb, Tm upconversion nanoparticles (UCNPs) and the analyte-triggered cascade signal amplification (CSA) technique. The construction of the sensing system consisted of three processes. First, IO3− oxidized o-phenylenediamine (OPD) to diaminophenazine (OPDox), while IO3− was reduced to I2. Second, the generated I2 can further oxidize OPD to OPDox. This mechanism has been verified by 1H NMR spectra titration analysis and HRMS measurement, which effectively improves the selectivity and sensitivity of the measurement of IO3−. Third, the generated OPDox can effectively quench the fluorescence of UCNPs via the inner filter effect (IFE), realize analyte-triggered CSA, and allow quantitative determination of IO3−. Under the optimized conditions, the fluorescence quenching efficiency showed a good linear relationship to IO3− concentration in the range of 0.06–100 μM, and the detection limit reached 0.026 μM (3RSD/slope). Moreover, this method was applied to detect IO3− in table salt samples, yielding satisfactory determination results with excellent recoveries (95.5–105%) and high precision (RSD <5.5%). These results suggest that the dual-readout sensing strategy with well-defined response mechanisms has promising application prospects in physiological and pathological studies.